Wow. Gilbert claimed there was nothing conceivably dangerous in a kit which contained polonium 210. Hopefully it had a very small amount, given that the median lethal dose is a tenth of a microgram: https://en.wikipedia.org/wiki/Polonium#Biology_and_toxicity
Looks like a great gift for my younger brother. And if he doesn't end up using it I wouldn't mind making a tin hedgehog myself.
If you want a more fun science based kit, I would recommend Yum Science ( http://www.yumscience.com/ ). It combines cooking with science. Kids love it.